Analysis of AdSCR Systems for NOx Removal During the Cold-Start Period of Diesel Engines

A better understanding of the adsorption behaviors of hydrocarbons on adsorbent would help trap the hydrocarbons emitted from diesel engines during cold start period more efficiently. In this paper, the adsorption behaviors of hydrocarbons in LTA zeolite was studied using Grand Canonical Monte Carlo (GCMC) simulation. The adsorption isotherms and mass clouds are obtained for both pure component and binary mixtures under certain temperatures. The adsorption isotherms reveal that the average loading of ethylene and propylene has the similar trend. Both of them increase with the increase of pressure and decrease significantly with the increase of temperature. The binary mixtures show competitive adsorption behavior. Propylene is adsorbed much more strongly than ethylene in LTA zeolite. The obtained mass clouds show that propylene distributes in both the α cage and β cage of the LTA zeolite, while ethylene distributes mainly in the β cage of the LTA zeolite.

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A Fundamental Thermodynamic Study on the Effects of Engine Scale in Diesel Engines

ASME 2019 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2019-7121 ◽

2019 ◽

Author(s):

Kevin J. Burnett ◽

Ashwani K. Gupta ◽

Jim S. Cowart

Keyword(s):

Heat Transfer ◽

Surface Area ◽

Wall Temperature ◽

Diesel Engines ◽

Cold Start ◽

Cylinder Wall ◽

Piston Speed ◽

Heat Effects ◽

Wide Range ◽

Significant Difference

Abstract The Navy has a wide range of diesel engines with bore sizes varying by a factor of four. In general, diesel engines can have bore scaling over a full order of magnitude. As an engine cylinder gets larger its surface area to volume ratio reduces significantly, which in turn affects in-cylinder heat transfer. In this study, a fundamental generalized thermodynamic model of diesel engines was developed. The various key model effects were systematically analyzed along with engine bore size. Further, cylinder wall temperature was varied across a range of cold start to stabilized operating temperatures. The results of this study show that smaller bore diesel engines are always more sensitive to cold start conditions. The effect is reduced with increasing wall temperature yet smaller diesel engines have cooler end-of-compression temperatures as comparted to larger engines. The effects of engine speed, in which mean piston speed is held constant, tend to modestly reduce the differences between various size diesel engines due to non-linear heat transfer effects. When variable specific heat effects are correctly considered, end-of-compression air charge temperatures are only modestly different as a function of engine bore size. The most significant difference is the overall reduced heat transfer in larger engines due to the surface area to volume effect. A difference of a factor of three for in cylinder heat transfer relative to in-cylinder inducted air mass is predicted being much greater for the smaller engines. Higher exhaust temperatures are also characteristic of the larger bore engines. This allows more combustion work to be delivered to the piston with a correspondingly higher thermal efficiency for larger diesel engines. Future work will evaluate fuel effects on varying bore size.

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Perovskite-Based Catalysts as Efficient, Durable, and Economical NOx Storage and Reduction Systems

Catalysts ◽

10.3390/catal10020208 ◽

2020 ◽

Vol 10 (2) ◽

pp. 208

Author(s):

Jon A. Onrubia-Calvo ◽

Beñat Pereda-Ayo ◽

Juan R. González-Velasco

Keyword(s):

Removal Efficiency ◽

Diesel Engines ◽

Nox Reduction ◽

Platinum Group Metals ◽

Nox Storage ◽

Automotive Application ◽

Nox Removal ◽

Nox Storage And Reduction ◽

Nox Storage Capacity ◽

Nox Removal Efficiency

Diesel engines operate under net oxidizing environment favoring lower fuel consumption and CO2 emissions than stoichiometric gasoline engines. However, NOx reduction and soot removal is still a technological challenge under such oxygen-rich conditions. Currently, NOx storage and reduction (NSR), also known as lean NOx trap (LNT), selective catalytic reduction (SCR), and hybrid NSR–SCR technologies are considered the most efficient control after treatment systems to remove NOx emission in diesel engines. However, NSR formulation requires high platinum group metals (PGMs) loads to achieve high NOx removal efficiency. This requisite increases the cost and reduces the hydrothermal stability of the catalyst. Recently, perovskites-type oxides (ABO3) have gained special attention as an efficient, economical, and thermally more stable alternative to PGM-based formulations in heterogeneous catalysis. Herein, this paper overviews the potential of perovskite-based formulations to reduce NOx from diesel engine exhaust gases throughout single-NSR and combined NSR–SCR technologies. In detail, the effect of the synthesis method and chemical composition over NO-to-NO2 conversion, NOx storage capacity, and NOx reduction efficiency is addressed. Furthermore, the NOx removal efficiency of optimal developed formulations is compared with respect to the current NSR model catalyst (1–1.5 wt % Pt–10–15 wt % BaO/Al2O3) in the absence and presence of SO2 and H2O in the feed stream, as occurs in the real automotive application. Main conclusions are finally summarized and future challenges highlighted.

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